1. Field of the Invention
The invention relates to a voltage switching device.
2. Description of the Prior Art
A voltage switching device is also known from DE-C1 41 12 907, having voltage doubling circuits with two symmetrical circuit halves with switching options for the two operating states in the form of a power switch for incoming alternating voltage and two boost choppers essentially in symmetrical mirror image, one being disposed in each of the two symmetrical circuit halves of the voltage doubling circuit. Again, the disadvantage of this arrangement is that the two storage elements of the boost choppers are directly connected to one another and again form a capacitive midpoint.
Voltage switching devices are also known which are used for activating switches for different powers. To this end, the voltage switching device is designed so that a separate switch group is provided for every possible voltage rating, in particular for 230 V and 400 V voltages, and once the delivered voltage has been evaluated a switching device switches to the corresponding switch group. The individual switch groups consists of a power rectifier and a storage element, for example.
The individual switch groups provided for the different voltages are connected in parallel with one another and a corresponding switch group is activated by a corresponding switching device. The disadvantage of this arrangement is that the individual switch groups have to be dimensioned separately from one another and the fact of having to use different components means that the cost of voltage switching devices of this type is relatively high.
The underlying objective of the present invention is to provide a voltage switching device which is capable of switching in a simple manner from one energy source with a corresponding voltage to another energy source with a different voltage.
This object is achieved by the invention with a voltage switching device comprising a power rectifier connected to a positive supply line and a negative supply line, a booster chopper arranged in each supply line, each booster chopper comprising a choke, a switching element, a diode and a storage element, at least one transformer having a primary winding and a secondary winding, and a switching device for switching the boost choppers in series or in parallel, depending on a voltage delivered by an energy source. The switching elements have inputs connected to a control device, and a plurality of mains leads connect the power rectifier to the energy source. A consumer is connected to the secondary winding of the transformer, a power evaluating device evaluates the value of the voltage delivered by the energy source. The power elvaulating device has an output connected to the switching device or the control device, a high frequency inverter is independently connected to each storage element, and each high frequency inverter is connected to the primary winding of the transformer.
The advantage of this arrangement is that because of the layout of the boost choppers, the flow of energy to the storage elements can be made symmetrical by controlling the boost choppers, thereby offering a simple approach to preventing a non-symmetrical supply of the downstream high frequency inverter. Another advantage resides in the fact that the use of boost choppers in the voltage switching device obviates the need for a capacitive voltage midpoint resulting from parallel or serial switching of the storage elements.